It’s Official: Sugar Is Way More Addictive Than Fat

What’s the more insidious part of the nutrition label: sugar or fat? It’s the age-old question, but startling new research in the American Journal of Clinical Nutrition finally has the answer.

Sorry, sugar-lovers.

In the admittedly delicious-sounding experiment, researchers fed 106 lean adolescents chocolate milkshakes with varying fat/sugar ratios. Brain imaging revealed that fat and sugar affect different parts of the brain. High-fat milkshakes lit up the regions linked to associative learning and somatosensory regions. But high-sugar shakes caused a frenzy in the regions associated with reward, motivation, and taste.

That helps explain why sugar can be so addictive—and why sugar is associated with signs of withdrawal, but fat isn’t. Interestingly, sugar’s potent hold on our brains seems to grow with each dose; when the scientists increased the fat content of the shakes, brain activation remained the same. But when they cranked up the sugar, reward centers kept getting more and more stimulated.

The results suggest that we should prioritize reducing sugar over reducing fat, the study authors write. Sweetness is a primary reward—our brains are evolutionarily predisposed to seek sugar—while fat is more of a texture, through which early conditioning shapes our preferences. In other words, we have more control over fat than we do sugar.

And interestingly, the researchers didn’t find a relationship between sugar and fat in activating the brain, even though they’re often paired in unhealthy treats (and equally blamed for dessert aftermath).

“Sugar addiction is a very real thing,” says Travis Stork, MD, cohost of TV’s The Doctors and author of The Doctor’s Diet. (Dr. Stork was not involved with the study.) “It can rewire our brains and our reward pathways to such an extent that we become more primitive in our wants and desires…and unfortunately, the more of it we eat, the less control we have over that addiction, not unlike drugs or alcohol or smoking.”